On August 17th, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detector observed gravitational waves produced by the merger of two neutron stars for the first time ever. Only hours after LIGO made the announcement to a large community of astronomers, around 70 observatories and telescopes were pointed towards the sky to catch what they could of the event, making it one of the most observed astronomical events in history. This observation marks the first time we see gravitational waves from something other than a black hole binary. It was also the first sighting of heavy elements being formed and the first ever measurement of the universe’s expansion using gravitational waves.
Having measurements from several different phenomena gives different perspectives of the same event and means that astronomers and astrophysicists will be working collaboratively to make advances that they may not have been able to otherwise. Not only does this event confirm many long-predicted theories, it also provides data that is richer than anyone could have hoped for.
This momentous event had important contributions from two members of the University of Bath’s Physics Department. Dr Hendrick van Eerten, a computational astrophysicist and one of the lead authors on the study, led the theoretical input to one of the studies by creating models that could trace the gravitational wave source to Gamma Ray Bursts (GRB), and thus confirm the prediction that X-rays would eventually be detected despite their speed and direction of expulsion. Professor Carole Mundell, a co-author on a related paper declared that the technology to observe light from such an event had long been available, but that no one could have expected that it would be successful for many years.
While LIGO has detected gravitational waves from the merger of black hole pairs, it is the first time it detects some from the merger of neutron stars. Neutron stars are small, very dense stars that have long been predicted to produce short gamma ray bursts (SGRB) upon their merging. SGRBs are a kind of GRB, and are one of the brightest events ever observed in our Universe. They are so bright and energetic, that they can help us see back into the very distant Universe, and potentially back to what astronomers and astrophysicists call the “Dark Ages” – a period between the Big Bang and about 1 billion years after it. Although Gamma Ray Bursts are extremely bright, their prompt emission is short lived, and thus difficult to observe. Thus, the detected gravitational waves acted as a ‘warning’ to a community of astronomers for them to point their telescopes and instruments in the right direction to observe the SGRB in time. Multi messenger astronomy is sure to reveal many more exciting observations in the future. In particular, seeing back in time back to the “Dark Ages”, which we know very little about, could potentially unlock some of the answers to our biggest questions about the Universe and help physicists understand the how’s and why’s of the creation of our Universe.